Production of color film having a silver sound track



Feb. 18, 1941. J EGGE'RT ETAL 2,232,056

' PRODUCTION OF COLOR 'FILM HAVING A SILVER sowun TRACK Filed Nv. 26, '19s? lllI/l/ I Ill" \lllllllllll John E qgert Friedrich Niasen In vemors Hans By TheirAflorneys Patented Feb. 18,

UNlTllD STATES PATENT OFFICE PRODUCTION OF COLOR FILM HAVING A SILVERSOUNDTBACK Delaware Application November 26, 1937, Serial No. 176,668 In Germany December 2, 1936 '1 Claims. (or as -2y Our present invention relates to the produc- -tion of color film having a silver sound track.

One of its objects is to provide an improved process of producing a color sound film the color images of which are produced by color forming development. Another object is to provide an improved apparatus for producing such color sound films. Further objects of the invention f will appear from the detailed description following hereafter. Reference is made to the. accompanying drawing in which:

Figure 1 shows a perspective view of the apparatus constructed in accordance with andembodying a preferred form of our invention.

Figures 2 and 3 are detailed longitudinal sectional views of the apparatus shown in Figure 1.

'In making picture and sound films in which a color photographic process is used for producing the pictures, the difilculty arises that unless special precautions are taken the sound track is also produced .in color in the finished film. Since the photo-electric cells of the sound reproducing apparatus do not respond to colored light in the same manneras to thecontrasts of a blackand-white sound track various difliculties arise in the reproduction of the'sound. In particular it is desirable to produce the sound track in silver, since the photo-electric cell is considerably more sensitive to the high contrasts in transparency of a silver image than to those of a color image. It is particularly essential to produce a silver sound track in multi-layer color sound films in which the color sensations are developed by color forming development and the silver image, is subsequently completely removed@ According to our invention the desired silver.

- sound track is produced in a color picture and sound film in which the color sensations are developed by color forming development by sub-.

jecting before the removal of the residual silver bromide image resulting from the color form- If ing development either the strip of film carrying the sound track or that carryingthe picture image to a fresh exposure, whilst that part of the film whichjs not to be exposed is masked. For example,'the silver produced in the color forming development (in the picture and sound images) bromide can then be developed; or the residual silverhromide can be converted into silver iodide can be converted into silver chloride and the sound track can .be subjected to an exposure of the. correct magnitude, so thatonly the silver sound track can, for example,-be masked during the second exposure of the picture area, the sil 6 ver removed and the-residualsound track consisting of silver bromide exposed and developed. Or the silver produced in the development of the color picture can be converted into silver chloride, the sound. strip of the film subjected to a 10 calculated exposure, the silver bromide developed to silver-and the silver chloride removed by fixing. Another procedure applicable in cases in which the color picture is produced by the reversal process is as inflows: 15

After the second exposure of the picture record, the film is developed, the residual silver bromide in the sound track is converted into silver iodide, the developed silver is converted into silver chloride or silver-bromide and removed 20 by fixing and the silver iodide sound track is blackened by any known process.

By another'teature of the invention the steps in these processes are conducted in an afterexposure apparatus in which the film passes around a hollow drum within which is arranged a source of light. The apparatus is preferably specially adapted for the process of the invention by the'provision of a drum consisting of interchangeable cylindrical rings which are 're- 30 'spectively transparent and opaque. The drum is layer film a negative in which the colors are complementary to those of the original; this negative is then copied on a three-layer positive 40 film and developed in color, the silver precipitate is bleached and the film fixed. If now the sound track is copied as usual onto the same film and treated in the same manner as the picture,

a color track on a transparent background is'dli obtained. An effective sound track can be obtained in accordance with the invention in thef following manner:

The picture and sound records are printed in the usual manner, the print is developed in color, the silver bleached without removal of the remaining silver bromide, the sound track is exposed a second time, if necessary to a calculated extent, and .the print is developedin a usual developer and fixed. 'There are thus obtained -a F.

5 silver sound track and a complementary color sound track. The sound track is preferably printed with light of such color that the color image of the sound track obtained transmits light to which the photo-electric cell is sensitive. In" this case the second exposure must be effected so that thesilver sound track is produced in the same layer as that in which the color sound track was firstproduced. In this case therefore the sound track is subjected to a reversal development. a If the finished color sound film is to be produced by a reversal process and not by printing from used: g

The second. exposure in'the reversal process may be so conducted that the picture image of the film is exposed whilst the sound track is masked by a diaphragm. No silver is then formed in the sound track in the second development. The silver is then dissolved as in the normal reversal process, the sound track consisting of 'a residual silver bromide image. After dissolution of the silver, the silver bromide in the sound .track is exposed and blackened by a further development. The process is completed by fixing the remaining silver bromide and the like in the tive process.

usual manner.

This process can thus always be used if, in the production of color sound films a second exposure is used and the developed silver is dissolved. In contradistinction to processesin which a coating of a lacquer or the like is used this method of producing the sound track has the advantage that it includes no stage w ch can lead to contamination of the film or the baths.

In some processes, the silver developed inthe picture layer is re-converted into a silver halide,

developed silver chloride can be removed simply by fixing. It is advantageous to insert in the path of the light during the exposure a, filter which is opaque to ultra-violet light, which alone renders silver chloride capable of development. In order to avoid fogging the picture it is advantageous to mask the light for producing. the final blackening so that it falls only on the' sound track.

- A corresponding process for producing a silver sound track is also possible in the negative-posi- For example, after the, color forming development and the chlorination of the silver the remaining silver bromide can be made capable of-development by a. renewed exposure without affecting the chloride. One half of the sound track' then consists of a color image, and the other adjacent half of a silver image. Only a negligible quantity of light is absorbed by the dyestuff so that its presence does not interfere with the sound reproduction. If the dyestufi were strongly absorbent a silver sound track would be unnecessary, so that in that case the special treatment of the silver bromide would be unnecessary. Silver chloride is, however, generally already capable of being blackened by a developer even when unexposed so that theprocess described is subject to a certain limitation.

a negative, the following, method may be exposed. The silver is then converted into silver bromide and subjected to another development. Only the silver bromide which was exposed before the bromination can be blackened by this development. After fixing, a silver sound track is obtained.

Another method is as follows:

If the second development has been conducted without causing development of the silver bromide of the sound track, it is possible to convert this bromide into silver iodide. For this purpose use may be made of the known Renwick solution which "contains potassium iodide, sodium sulfite and thiosulfate. It is known that silver iodide is considerably more dimcult to fix than silver chloride or bromide. If the silver still present is then converted into silver chloride or bromide, this can be fixed with the aid of a usual fixing bath. The sound track is then obtained in silver iodide and can be used as such for sound reproduction. It is, however, better to develop this silver iodide or to blacken it, for example by sulfiding, so that a silver sulfide sound track is obtained. Since only silver iodide is to be blackened, a developer .can be used which is relatively powerful, this being necessary because silver iodide is more difficult to develop than silver chloride.

In order to be able to conduct efiiciently the various exposures, namely, the exposure of the sound track without the picture and the'exposure oi' the picture without the sound track, there may be used the exposure apparatus illustrated in the accompanying drawing.

The film l to be illuminated is guided as shown in Figure 1 by guide rollers 2 .and 3 around a drum 4, preferably hollow, which has, as it is to 'be seen in Figure 2, a transparent cylindrical ring I and an opaque portion 8; The transparent portion and the opaque portion areinterchangeably connected in such a manner that the transparent portion 5 can be exchanged for an opaque portion 6? and the opaque portion 6 for a transparent portion 5' (Fig. 3). These portions may be joined, for example, by a screw thread,

bayonet Joint or the like.

tion extends as far as it is should be exposed. The exposure, is effected by a lamp 1 in the interior of the drum 4, 5, 6. At the points at which the film comes into contact with and leaves the drum there are provided means for preventing undesired exposure, for example a diaphragm 8 (Figures 1 and 3). Since part of the light penetrates the film means must The transparent pordesired that the mm be provided for preventing this light from .'reaching a point at which it can again fall on the film.

This is most easily attained by painting a matt black the container 9 in which the whole apparatus is enclosed under water and in which the exposure occurs.

guide 4 is mounted so that it is laterally movable. The exposure is made as farlas possible under Or a strip'of black material may 3 be passed through the apparatus in contact with on water in order to obtain good optical contact. In

this case the lamp must be protected from the water, for example by meansof a glass container.

- This glass container can be designed to screen oil'- false illumination, for example by a metallic re-;

flecting coating. By thismeans the best possible use is made of the light. If desired, for particular purposes the container may be made of colored glass or provided with a filter layer.

What we claim is:

1. In a process of producing a. silver sound track in a color sound film comprising silver bromide emulsion layers in which the color images are produced by a color development method wherein color formers are reacted with the oxidation product of an aromatic color developer, the improvement which comprises forming latent picture records and sound records, transforming at least one of said records into silver and color images in said color developer, converting silver in said records to a different silver halide, re-

exposing the residual silver bromide of the sound track, converting the latent ima e in the sound track to a real image with a developer having no effect on said'silver halide and fixing to remove silver halide.

2. In a process of producing a silver sound track in a color sound film comprising silver bromide emulsion layers in which the color images are produced by a color development method wherein color formers are reacted with the oxidation product of an aromatic color developer, the improvement which comprises forming latent picture records and sound records, transforming said records into silver negative images in an ordinary developer, re-exposing the residual sil ver bromide of said picture records to form latent positive picture images while maskingsaid sound records, transforming said latent positive images into silver and color positive picture imagesin said color developer, converting the silver in all said records into a different silver halide, re-exposing the residual silver bromide of the sound track without substantially affecting said silver halide, converting the resulting latent image in the sound track to a real silver image with a developer having substantially no effect on such different silver halide, and fixing to remove said silver halide.

3. In a process of producing a silver sound track in a color sound film comprising silver bro- 'ide by fixing.

mide emulsion layers in which the color images are produced by a color development method wherein color formers are reacted with the oxidation product of an aromatic color developer, the improvement which comprises. forming latent positive picture records and negative sound records, transforming said'records into corresponding silver and color images in saidcolor developer, converting silver in said records to a difierent silver halide, re-exposing the residual silver bromide of the sound track without substantially affecting said silver halide, converting the resulting latent image in the sound track to a positive silver image with a developer having substantially no efiect on said different silver halide and fixing to remove said silver halide.

4. In a process of producing "a silver sound track in acolor sound film comprising silver bromide emulsion layers in which the color images are produced by a color development method wherein color formers arereactedwlth the oxidation product of anaromatic color developer,

, the improvement which comprises forming latent picture records and sound records, transforming said records into silver and color images in said color developer, subjecting before the removal of the residual silver bromide images resulting from said color development the picture records to a second exposurewhilst the sound records are masked, exposing the residual silver bromide image of the sound tracks, converting the silver produced by the color development into a different silver halide, developing the residual silver bromide image of the sound tracks with a developer having substantially no effect on said different silver halide, and removing the silver hal- 5. The process defined in claim 1 where said different silver halide is silver chloride.

6. The process defined in claim 2 where said different silver halide is silver'chloride.

'7. The process defined in claim 3 where said different silver halide is silver chloride.

JOHN EGGERT. FRIEDRICH NISSEN. 

